An offset in TEX86 values between interbedded lithologies: Implications for sea-surface temperature reconstructions

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms) sea-surface temperature (SST) proxy is based on the distribution of isoprenoid glycerol dialkyl glycerol tetraether (GDGT) membrane lipids of pelagic Thaumarchaeota that are preserved in marine sediments. It is a valuable tool for reconstructing past SSTs from sedimentary archives; however there are still major uncertainties as to the effects of variables other than temperature on the proxy. Here we present the first study of GDGT variability across early Cretaceous interbedded pelagic and shelf-sourced turbiditic sediments from two Deep Sea Drilling Project (DSDP) sites in the western North Atlantic. The results indicate that a small, but consistent, offset in TEX86 ratios, equivalent to ~ 1–2 °C of temperature difference, occurs between interbedded lithologies of a similar age. The offset can be attributed to spatial differences in sea-surface temperatures or thaumarchaeotal populations between the shelf and the open ocean, or to secondary diagenetic effects related to oxic degradation of the GDGTs. Of these, a difference in either thaumarchaeotal taxa or ecology between those living in the shelf and ocean areas seems most plausible. Regardless of the root cause of the offset, these findings highlight the necessity of careful sample selection prior to TEX86 analysis, to ensure robust interpretation of palaeotemperature trends.Thanks to Alexandra Nederbragt for her assistance with TEX86 analysis, and to Richard Pancost and Jennifer Biddle for their helpful discussions which greatly improved this manuscript. Thanks to Annette Bolton for her assistance with PCA in SPSS. We are grateful to the two anonymous reviewers for their thoughtful and detailed comments. Thanks to Alex Wülbers and Walter Hale at the Bremen Core Repository for their core-sampling assistance. This research was funded by a NERC studentship (K.L.) and a Royal Society University Research Fellowship (S.A.R.). Samples were provided by the Integrated Ocean Drilling Program (IODP)

A republic of consumers: Jo Littler in discussion with Clive Barnett and Kate Soper

Clive Barnett is a human geographer at the Open University and is part of a team working on a project entitled ‘Governing the Subjects and Spaces of Ethical Consumption’. Kate Soper, a professor of philosophy and a cultural theorist based at London Metropolitan University, is working with Lyn Thomas on their ‘Alternative Hedonism and the Theory and Politics of Consumer Culture’ project.1 Jo Littler interviewed them both about the cultural and political implications of the expansion of green, ethical and anti-consumerism

Climate and carbon-cycling in the Early Cretaceous

The Cretaceous (~145–65 Ma) is widely regarded as a greenhouse period with warm, equable climates and elevated atmospheric CO2 relative to the modern. However, the earliest Cretaceous (Berriasian–Barremian; 145–125 Ma) is commonly characterised as a relatively colder “coolhouse” interval, typified by lower global temperatures than the mid-Cretaceous. Unfortunately, the lack of absolute sea surface temperature (SST) estimates prior to the Barremian has hampered efforts to definitively reconstruct Early Cretacous climate. Here, the TEX86 palaeotemperature proxy, for which a detailed review is provided, has been used to generate a 13 myr record of SST estimates for the Early Cretaceous, based on sediments from assorted deep-sea drilling sites. A consistent offset in the TEX86 ratio between transported mudstones and pelagic carbonates in the low-latitude marine sediments (DSDP Sites 603 and 534) has been identified, which may be linked to post-burial diagenesis or a difference in organic matter type between lithologies. Mindful of these apparent lithological effects on TEX86, only the pelagic sediments were used to subsequently reconstruct Early Cretaceous SSTs. These TEX86 records demonstrate both elevated SSTs (>27 ºC) at low and mid-latitudes relative to the modern, and the apparent stability of these high temperatures over long timescales. This lack of SST variation in the low-latitudes during the Valanginian positive carbon-isotope event (CIE; ~135–138 Ma), casts doubt on the warming-weathering feedback model put forward to explain this major perturbation. Additionally, new paired bulk organic (δ13Corg) and bulk carbonate (δ13Ccarb) carbon-isotope records from North Atlantic DSDP sites, have been used to reconstruct relative changes in pCO2 across the CIE. These observed fluctuations in Δ13C imply changes in carbon-cycling and a possible drawdown in CO2, due to excess organic matter burial associated with the CIE

A high‐resolution benthic stable‐isotope record for the South Atlantic: implications for orbital scale changes in Late Paleocene–Early Eocene climate and circulation

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The Late Paleocene and Early Eocene were characterized by warm greenhouse climates, punctuated by a series of rapid warming and ocean acidification events known as “hyperthermals”, thought to have been paced or triggered by orbital cycles. While these hyperthermals, such as the Paleocene Eocene Thermal Maximum (PETM), have been studied in great detail, the background low-amplitude cycles seen in carbon and oxygen-isotope records throughout the Paleocene–Eocene have hitherto not been resolved. Here we present a 7.7 million year (myr) long, high-resolution, orbitally-tuned, benthic foraminiferal stable-isotope record spanning the late Paleocene and early Eocene interval (∼52.5–60.5 Ma) from Ocean Drilling Program (ODP) Site 1262, South Atlantic. This high resolution (∼2–4 kyr) record allows the changing character and phasing of orbitally-modulated cycles to be studied in unprecedented detail as it reflects the long-term trend in carbon cycle and climate over this interval. The main pacemaker in the benthic oxygen-isotope (δ18O) and carbon-isotope (δ13C) records from ODP Site 1262, are the long (405 kyr) and short (100 kyr) eccentricity cycles, and precession (21 kyr). Obliquity (41 kyr) is almost absent throughout the section except for a few brief intervals where it has a relatively weak influence. During the course of the Early Paleogene record, and particularly in the latest Paleocene, eccentricity-paced negative carbon-isotope excursions (δ13C, CIEs) and coeval negative oxygen-isotope (δ18O) excursions correspond to low carbonate (CaCO3) and coarse fraction (%CF) values due to increased carbonate dissolution, suggesting shoaling of the lysocline and accompanied changes in the global exogenic carbon cycle. These negative CIEs and δ18O events coincide with maxima in eccentricity, with changes in δ18O leading changes in δ13C by ∼6 (±5) kyr in the 405-kyr band and by ∼3 (±1) kyr in the higher frequency 100-kyr band on average. However, these phase lags are not constant, with the lag in the 405-kyr band extending from ∼4 (±5) kyr to ∼21 (±2) kyr from the late Paleocene to the early Eocene, suggesting a progressively weaker coupling of climate and the carbon-cycle with time. The higher amplitude 405-kyr cycles in the latest Paleocene are associated with changes in bottom water temperature of 2–4 °C, while the most prominent 100 kyr-paced cycles can be accompanied by changes of up to 1.5 °C. Comparison of the 1262 record with a lower resolution, but orbitally-tuned benthic record for Site 1209 in the Pacific allows for verification of key features of the benthic isotope records which are global in scale including a key warming step at 57.7 Ma.Thanks to Alexis Kersey for picking foraminifera and assisting with sample processing (at UCSC), and to Walker Weir, Alejandro Aguilar, and Phillip Staudigel for lab assistance, and to Dyke Andreasen and Chih-Ting Hsieh for stable-isotope support (UCSC). Thanks to Barbara Donner (MARUM) for coordinating foraminifera picking, and to Monika Segl and her team (MARUM) for stable-isotope analyses. We thank Roy Wilkens (Hawaii) for core images analysis. Sediment samples were supplied by the Ocean Drilling Program. Funding for this project was provided by NSF grant (grant number EAR-0628719) to J.Z. and DFG grants (RO 1113/2 through RO 1113/4) to U.R

Orbital forcing of the Paleocene and Eocene carbon cycle

This is the final version of the article. Available from the publisher via the DOI in this record.Multimillion-year proxy records across the Paleocene and Eocene show prominent variations on orbital time scales. The cycles, which have been identified at various sites across the globe, preferentially concentrate spectral power at eccentricity and precessional frequencies. It is evident that these cycles are an expression of changes in global climate and carbon cycling paced by astronomical forcing. However, little is currently known about the link between orbital forcing and the carbon cycle-climate system and the amplitude of associated atmospheric CO2 variations. Here we use simple and complex carbon cycle models to explore the basic effect of different orbital forcing schemes and noise on the carbon cycle. Our primary modeling target is the high-resolution, ∼7.7 Myr long, benthic isotope record at Ocean Drilling Program Site 1262 in the South Atlantic. For direct insolation forcing (as opposed to artificial eccentricity-tilt-precession), one major challenge is understanding how the system transfers spectral power from high to low frequencies. We discuss feasible solutions, including insolation transformations analogous to electronic AC-DC conversion (DC’ing). Regarding mechanisms, we focus on tropical insolation and a long-term carbon imbalance in terrestrial organic burial/oxidation but do not rule out other scenarios. Our analysis shows that high-latitude mechanisms are unlikely drivers of orbitally paced changes in the late Paleocene-early Eocene (LPEE) Earth system. Furthermore, we provide constraints on the origin and isotopic composition of a possible LPEE cyclic carbon imbalance/source responding to astronomical forcing. Our simulations also reveal a mechanism for the large 13C-eccentricity lag at the 400 kyr period observed in Paleocene, Oligocene, and Miocene sections. We present the first estimates of orbital-scale variations in atmospheric CO2 during the late Paleocene and early EoceneThis research was supported by U.S. NSF grants OCE12-20615 and OCE16-58023 to R.E.Z. and J.C.Z. and the Deutsche Forschungsgemeinschaft (DFG) to T.W

The media and climate change

Progressive voices in the arts and heritage sector have called for a politics of cultural democracy as a means of empowering all to participate in public life. Through a rejection of policies of 'inclusion', they have asked more searching questions about the role culture can play in the fight for social justice. At the same time the sector is preparing for a change of ideological direction, as rumours run rife about what a future Tory government, highly critical of state intervention, will do to the bodies that run the arts and heritage sector. This article looks at the prospects for a radical cultural democracy in the face of these potential political changes

Comparison of sediment composition by smear slides to quantitative shipboard data: a case study on the utility of smear slide percent estimates, IODP Expedition 353, northern Indian Ocean

This is the final version. Available on open access from Copernicus Publications via the DOI in this record. Data availability. All primary data in this paper (smear slide estimates, coulometer CaCO3, NGR, and photomicrographs) generated during shipboard operations of IODP Expedition 353 are available online as part of the IODP LIMS Online Report Portal: https://web.iodp.tamu.edu/LORE/ (International Ocean Discovery Program JOIDES Resolution Science Operator, 2021). K, U, and Th contents quantified from NGR spectra are available in the EarthChem data library (https://doi.org/10.1594/IEDA/100668, DeVleeschouwer, 2017)Sample availability. All IODP Expedition 353 cores, including sites U1443, U1446, and U1448, are archived at the IODP repository at the Kochi Core Center (http://www.kochi-core.jp/en/ iodp-curation/index.html, last access: 6 December 2021).Abstract. Smear slide petrography has been a standard technique during scientific ocean drilling expeditions to characterize sediment composition and classify sediment types, but presentation of these percent estimates to track downcore trends in sediment composition has become less frequent over the past 2 decades. We compare semi-quantitative smear slide composition estimates to physical property (natural gamma radiation, NGR) and solid-phase geochemical (calcium carbonate, CaCO3 %) measurements from a range of marine depositional environments in the northern Indian Ocean (Bay of Bengal, Andaman Sea, Ninetyeast Ridge) collected during International Ocean Discovery Program (IODP) Expedition 353. We show that presenting smear slide estimates as percentages, rather than abundance categories, reveals similar downcore variation in composition to the more quantitative core analyses. Overall downcore trends in total calcareous components from smear slides (foraminifers + nannofossils + shell fragments + authigenic carbonate) follow similar downcore trends to samples measured by CaCO3 coulometry. Total lithogenic components (clay + mica + quartz + feldspars + lithic grains + vitric grains + glauconite + heavy minerals + iron oxides) and clay from smear slides track reasonably well with NGR measurements. Comparison of site averages of absolute percentages of total calcium carbonate from coulometry and total calcareous components from smear slide observations reveals an overestimation in carbonate percentages in smear slides (likely due in part to underestimation of the clay fraction), especially in sediments rich in smectite clays. Differences in sediment color between sites and settling of clay particles during slide preparation may contribute to this discrepancy. Although smear slide estimates range in accuracy depending on the training of the operator, we suggest that sedimentologists describing cores obtained during scientific drilling can use the percent estimates of sedimentary components in smear slides to identify trends and cyclicity in marine sediment records

Solar total and spectral irradiance reconstruction over the last 9000 years

Changes in solar irradiance and in its spectral distribution are among the main natural drivers of the climate on Earth. However, irradiance measurements are only available for less than four decades, while assessment of solar influence on Earth requires much longer records. The aim of this work is to provide the most up-to-date physics-based reconstruction of the solar total and spectral irradiance (TSI/SSI) over the last nine millennia. The concentrations of the cosmogenic isotopes 14C and 10Be in natural archives have been converted to decadally averaged sunspot numbers through a chain of physics-based models. TSI and SSI are reconstructed with an updated SATIRE model. Reconstructions are carried out for each isotope record separately, as well as for their composite. We present the first ever SSI reconstruction over the last 9000 years from the individual 14C and 10Be records as well as from their newest composite. The reconstruction employs physics-based models to describe the involved processes at each step of the procedure. Irradiance reconstructions based on two different cosmogenic isotope records, those of 14C and 10Be, agree well with each other in their long-term trends despite their different geochemical paths in the atmosphere of Earth. Over the last 9000 years, the reconstructed secular variability in TSI is of the order of 0.11%, or 1.5 W/m2. After the Maunder minimum, the reconstruction from the cosmogenic isotopes is consistent with that from the direct sunspot number observation. Furthermore, over the nineteenth century, the agreement of irradiance reconstructions using isotope records with the reconstruction from the sunspot number by Chatzistergos et al. (2017) is better than that with the reconstruction from the WDC-SILSO series (Clette et al. 2014), with a lower chi-square-value

Mothers behaving badly: chaotic hedonism and the crisis of neoliberal social reproduction

This article focuses on the significance of the plethora of representations of mothers ‘behaving badly’ in contemporary anglophone media texts, including the films Bad Moms, Fun Mom Dinner and Bad Mom’s Christmas, the book and online cartoons Hurrah for Gin and the recent TV comedy dramas Motherland, The Let Down and Catastrophe. All these media texts include representations of, first, mothers in the midst of highly chaotic everyday spaces where any smooth routine of domesticity is conspicuous by its absence; and second, mothers behaving hedonistically, usually through drinking and partying, behaviour that is more conventionally associated with men or women without children. After identifying the social type of the mother behaving badly (MBB), the article locates and analyses it in relation to several different social and cultural contexts. These contexts are: a neoliberal crisis in social reproduction marked by inequality and overwork; the continual if contested role of women as ‘foundation parents’; and the negotiation of longer-term discourses of female hedonism. The title gestures towards a popular British sitcom of the 1990s, Men Behaving Badly, which popularized the idea of the ‘new lad’; and this article suggests that the new lad’s counterpart, the ladette, is mutating into the mother behaving badly, or the ‘lad mom’. Asking what work this figure does now, in a later neoliberal context, it argues that the mother behaving badly is simultaneously indicative of a widening and liberating range of maternal subject positions and symptomatic of a profound contemporary crisis in social reproduction. By focusing on the classed and racialised dynamics of the MBB – by examining who exactly is permitted to be hedonistic, and how – and by considering the MBB’s limited and partial imagining of progressive social change, the article concludes by emphasizing the urgency of creating more connections between such discourses and ‘parents behaving politically’

Correspondence: No substantial long-term bias in the Cenozoic benthic foraminifera oxygen-isotope record

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